Battery backed emergency lighting systems require a considerable amount of routine monitoring and testing to ensure proper operation in the event of an emergency. The batteries have a finite life so users must be aware when replacement is due. The battery back-up requires occasional testing to check battery health and system readiness. Previously, such systems have relied on time consuming manual inspection, but more recently testing can be achieved using Digital Addressable Lighting Interface (DALI) or Zigbee communication interfaces.
However, DALI and Zigbee have a number of problems and limitations. For example, DALI only allows 64 slave nodes per master. This may result in the need for multiple master controllers in a large system. In addition, DALI requires wiring between each light for communication. Hence building a DALI system has the inconvenience of running cables through ceilings and walls.
Zigbee is a wireless communication system, with the disadvantage of a limited range. This is especially true in buildings containing a large amount of metal. Repeaters may be used to extend the range of Zigbee, however this adds additional cost and complexity to the Zigbee system. This can make the system complicated and make debugging communications problems difficult.